JP2006-187063A discloses, as a fastening mechanism of a core and a shaft in which a large number of electromagnetic steel sheets constituting a rotor of a rotating electrical machine are stacked in layers, a fastening mechanism in which end plates arranged on both side surfaces of the core are directly pressed into the shaft and fixed thereto.
This is achieved by a mechanism in which a collar is interposed between the core and the shaft that are constituent elements of the rotor and in which the shaft and the collar, and the collar and core are pressed and fastened with a predetermined clearance. On both side surfaces of the core, the end plates directly pressed into the shaft are arranged. When the core and the end plates are formed with a silicon steel sheet and the shaft is formed with a steel rod, the collar is formed of a non-ferrous metal material such as a magnesium alloy that has a higher linear expansion coefficient than at least the core and the shaft. Thus, even if the individual elements are thermally expanded under a high temperature environment, a clearance of the collar with respect to the shaft in a direction in which a diameter is reduced is acquired.